1. Technical Field
The technical field relates to an imaging device, and more particularly to an image capturing unit having an aperture value update function.
2. Description of the Related Art
Digital cameras and other such imaging devices have exploded in popularity in recent years. One type of digital camera is the digital single lens reflex camera. When a subject is viewed through the optical viewfinder of this digital single lens reflex camera, the light incident on the optical system (that is, the subject image) is reflected by a reflecting mirror disposed along the optical path, and is guided to the viewfinder optical system. As a result, the subject image is converted by a pentaprism or the like into an erect image, and the user can see the subject image formed by the optical system through the optical viewfinder.
Meanwhile, when the optical system is used to capture an image, the reflecting mirror is retracted from the imaging optical path. As a result, the viewfinder optical path is changed to the imaging optical path, and upon completion of the imaging, the reflecting mirror is instantly returned to its home position. With a single-lens reflex camera, this operation is the same regardless of whether the camera is a conventional silver halide camera or a digital camera.
However, imaging with an optical viewfinder is extremely difficult for novices who lack experience with digital camera photography.
In view of this, an imaging device has been proposed that has a monitor imaging mode (known as a live-view imaging mode) that allows the subject to be viewed on a liquid crystal monitor during imaging (see, for example, Japanese Laid-Open Patent Application 2001-125173).
This type of imaging device generally has an aperture value update function. In the monitor imaging mode, real-time images sequentially captured at a set aperture value are displayed on a display device. Accordingly, the subject field depth, which varies with the aperture value, can be confirmed through the display device.
However, when the aperture value is large, generally the subject field depth is greater and there is a relatively larger sharp portion within the image. Accordingly, with a contrast detection method in which an image signal is used to adjust the focal point, it is more difficult to designate the peak contrast value, and there is the risk that focal point adjustment will be less accurate. There is a need for an imaging device with which stable focal point adjustment is possible regardless of the aperture value prior to imaging.
Also, when images of various aperture value are checked, it is easier to confirm differences between images due to differences in aperture values when the image is in focus, but no such technique has yet been proposed.